1. Field of the Invention
This invention relates to the lightweight design of an improved reciprocating piston for an internal combustion engine and/or compressor, and more specifically to improved structures for an integral ring piston fabricated from carbon-carbon composite materials.
2. Description of the Related Art
Internal combustion, reciprocating engines used in aerospace, military, and transportation applications and compressors should be lightweight and capable of operating at elevated temperatures.
Conventional internal combustion engines and compressors employ pistons fabricated from cast-iron, steel, or aluminum alloys. In many applications, aluminum alloy pistons have replaced steel and cast-iron pistons because they are lighter and their use has a dramatic effect on reducing total engine weight. However, aluminum alloy pistons used in high speed airplane engines and lightweight diesel engines frequently fail due to severe thermal loads at elevated engine operating temperatures, i.e. above 600 degrees Fahrenheit (F).
Additionally, the high thermal conductivity and high specific heat of cast-iron and steel pistons result in considerable "through-the-wall" heat loss. Such heat loss reduces engine and compressor operating efficiency, especially with diesel engines.
Further, conventional pistons fabricated from steel or aluminum alloy have relatively high coefficients of thermal expansion, i.e. they expand when heated. To account for thermal expansion, a small clearance between the piston and the cylinder liner is required. This clearance creates a gap through which compression gases "blow by" the piston thereby polluting the environment and reducing engine operating efficiency. To arrest "blow by," conventional pistons employ a plurality of piston rings to seal the gap.